There are many various structures for the packaging of film in cartridges for both storage and to protect the film during use. Most of these structures enclose a continuous loop of film and provide some sort of sprocket to drive the film and a take up reel or reels with structure to guide the film inside the cartridge to avoid fouling. Some cartridges include an aperture or viewing means for the film and the film is guided by the aperture in a relatively flat orientation to ensure a sharp and clear image. Most cartridge structures also include some sort of mirror or glass prism to reflect the light from its point of entry through the film and out the aperture. An indirect path is normally required as the interior structure of the cassette prohibits the use of a direct or straight line light path.
If the cartridge structure provides an aperture, the film is presented either oriented for direct viewing or oriented for projection, but not in both orientations. The cartridge is usually designed with a specific application in mind and the structure included in the interior of the cartridge limits the ways in which the film may be routed and displayed at an aperture. In addition, structure in normally included within the cartridge for guiding the endless loop of film so that it does not foul at higher speeds of operation. This is especially important when the cartridges are used in motion picture films which are operated at higher speeds than film strips or slides.
Most cartridges are sealed after they are loaded with a loop of film and are not intended to be later re-opened for changing the film or the like. In fact, most cartridge structures are not capable of being loaded or unloaded without additional tools due to the complicated internal guides and mechanisms required to keep the film on track. While this may be an advantage, there are also times when it would be desirable to allow the owner of the cartridge to change the film contained therein. Unfortunately, most cartridges are not provided with this feature.
Another limitation that most cartridges have is that they require the use of additional structure to either view the film inside the cartridge or to project the film, depending upon the intended purpose of the cartridge. This both increases the cost to view or project the film and limits the versatility of the film once it is packaged inside any particular structure.
As is evident from the above, there is a great need for a film cartridge which will eliminate or solve these problems as well as provide additional features which were heretofore unavailable in the prior art. Applicant has developed a film cassette which satisfies this need. Applicant's cassette is suitable for storing and displaying a continuous loop of film for use either with a direct viewer or in a project mode of operation. The cassette consists essentially of a housing which has apertures extending the full width of the housing on opposing sides thereof which are aligned to provide a direct, straight line path for light during either the direct view mode or the project mode. It should be noted that a mirror or prism could be provided in applicant's cassette as the interior structure would not interfere with such an arrangement. Windows may be provided to seal the apertures and prevent the film and cassette interior from becoming contaminated.
The housing contains a dual film gate assembly which has slots on opposing sides for routing the film from one end of the cassette to the other. There are snap on front plates provided to hold the film against the back plates and which outline and define approximately a frame of the film for display to the aperture. A double sprocket drive is mounted on a shaft which extends through the side of the cassette and which may have finger or thumb wheels extending outside the housing to operate the shaft manually. Any other suitable structure may be attached to the shaft for either manual or motorized operation. The double sprocket drive has means to positively engage the film adjacent the two areas where the film is displayed as an aid in positioning the film within the film gate and also to maintain the relative spacing between opposing portions of the film. Detent means may be provided to index the film advance by the double sprocket drive and accurately position a full frame before the apertures. This guarantees that a substantially larger amount of film can be looped in the top end of the cassette which has a deeper interior than the bottom end of the cassette. The double sprocket also helps avoid fouling of the film during operation. The positive engaging structure may consist of a spoked sprocket and film having sprocket holes or any other method suitable for positively engaging the film. The film is easily loaded into the cassette by first forming an endless loop of film, threading the film through both sides of the dual film gate assembly, snapping on the front plates to capture the film within the film gates, aligning the film so that a substantially greater portion of the continuous loop is formed at the top, and then inserting the film into the housing which may then be either sealed for permanent storage or merely snapped shut or closed with structure allowing re-opening for later replacement of the film.
In an alternate embodiment, the apertures may extend only half the width of each side of the cassette or approximately one full width of a frame of film. The film is threaded through similar internal structure but is displayed at only one aperture in one side of the cassette. Thus only one frame of film is displayed by the aperture at any point in time but the portion displayed may be either directly viewed or the cassette turned over for projection. This is possible because of the straight line, direct light path provided by apertures in opposing sides of the cassette which allows equal access to either side of the film without interference from optical elements or mirrors.
An integral direct viewer may be provided which permits direct viewing of the film much as in a hand held slide viewer by holding the opposite side of the cassette up against a light source and viewing the film from the front of the cassette. The thumb wheel may be used to advance the film and the complete film may be shown thereby. The direct viewer is detachable and consists essentially of an extension with a suitable optical element provided in the far wall of the extension and positioned to align with the side of the cassette having the direct view orientation presented at the nearer aperture. The direct viewer may be provided with detent or friction means for positively positioning the viewer in either the operable position or the stored position. The direct viewer may also be provided with a detachable structure to allow it to be removed completely from the cassette for operation in the project mode.
A snap on light unit may be used to provide a source of light to view the film in the direct view mode. The light unit is detachable and consists essentially of a flat rectangular housing which contains a battery pack and transformer, a switch, a bulb, and a lens which is positioned to line up with the direct view aperture when mounted on the cassette.
Thus, applicant has developed a cassette structure which is unique in providing means to contain and present a continuous loop of film in both a direct view and in a project orientation with a straight line path for light. The relatively simple structure provides many additional benefits and features over those containing more complicated structure in the prior art. Some of these include the possiblity of reloading the cassette once it has been manufactured and shipped from the factory, a direct view attachment structure which is simple and relatively inexpensive, a manual advancing means which may also be adapted for use with a motor drive, structure to ensure a flat orientation of the film at the point that it is displayed through the aperture, a positive engagement of the film as it is advanced through the cassette by means of a push-pull double sprocket drive, loose coils of film which reduce the possibility of breaking or fouling during operation, an integral light chamber which enhances the viewability of the film, and an overall structure which is relatively simple and inexpensive to manufacture as well as assemble into a fully loaded cassette.
Other features and advantages of applicant's cassette are found in the brief description of drawings and detailed description of the preferred embodiment.